Hi!
While trying to implement "words", we ran into the question of how to build lists of lists. The trouble boils down to this:
test = []:[]
is no problem, just as
Prelude> []:[]:[]:[]
[[],[],[]]
works fine. Now trying to put the two together _is_ a problem:
testlist 1 = []:[]
testlist n = []:(testlist n-1)
No instance for (Num [[a]])
arising from a use of `testlist' at <interactive>:1:0-9
Possible fix: add an instance declaration for (Num [[a]])
In the expression: testlist 2
In the definition of `it': it = testlist 2
Can someone please explain, what is going on here?
Regards,
Torsten